Modern engines are works of art. If you pop a hood on the latest and greatest Porsche, you can sit there and admire the view for hours. We associate the car’s performance with its engine. Yet, the engine, no matter how powerful, won’t do you any good unless you can maintain the contact between the rubber and the road. Because of that, the car suspension is one of the most important systems on any vehicle.
Understanding how it works will make you a better driver and help you recognize why your car behaves the way it behaves when you accelerate, brake, and corner. This segment of the eEuroparts.com Car Owners’ Manual will help you do just that!
Grip and Comfort – The Main Job of Car Suspension
Being able to drive around in modern cars makes us incapable of appreciating just how important suspension is. We’ve had centuries of experience with fixed axle carriages and solid, wooden or metal wheels. Needless to say, commuting back in those days was not comfortable by modern standards.
As it turns out, mounting a wheel to a solid axle and then affixing that mechanical set to a passenger platform leads to several issues. More specifically, every pebble you run over will upset the whole system, causing the passengers to feel every road imperfection.
When you’re barely going 20mph, the lack of comfort is bearable. But once you get up to speed, every small bump becomes a major issue. One of the main reasons why automotive suspension exists and why it’s so complex, is to make driving a comfortable experience at relatively high speeds (compared to what was previously available).
The other reason why car suspension was invented has to do with performance. Controlling a vehicle depends on its ability to maintain contact with the road surface. In other words, the moment your wheel loses grip, you are no longer in control of your car.
When you press the gas pedal and accelerate, your vehicle is subject to horizontal acceleration. However, when you hit a bump on the road, you’re introducing vertical acceleration to the equation. The bump offsets the wheel, forcing it to move up. Without suspension, it’s not just the wheel that moves up, but the whole chassis/body of the vehicle. To combat this effect, engineers have developed the core suspension components.
How Does Car Suspension Work?
Most modern suspension systems are based around three main components — linkage, springs, and shock absorbers.
Linkage is your first point of contact between the wheel and the car. Links come in all kinds of shapes and sizes. Over the years, various designs have become popular, including but not limited to wishbones, straight links, and more. Wishbone suspension is arguably the go-to choice for most car designers these days.
There’s the legendary double-wishbone suspension that features two control arms — one on the top and one on the bottom of the wheel, which connect the knuckle to the chassis/body of the car. Although more complicated, this type of front suspension is associated with precision steering, better handling and generally superior performance.
The other common type of front suspension is the McPherson strut which utilizes only one control arm at the bottom, while the top control arm is eliminated in favor of a strut that bolts directly onto the knuckle.
With that said, there are many types of links including anti-roll bars. Anti-roll bars represent a solid link between two slides of an independent suspension system. The purpose of the anti-roll bar is to reduce the body roll of the car as you’re steering through corners. By doing so, you’re getting a much better tire-to-road contact and hence better handling as well as more precise steering.
Springs are the key component when it comes to ensuring a smooth ride. Automotive springs come in a variety of different shapes. Modern passenger and performance cars generally use coil springs or torsion bars to provide some cushioning when as you run over road imperfections. Commercial vehicles designed to carry heavy loads usually run coils in the front and leaf springs in the back.
Modern automotive springs play a major role in performance as well. Spring rate is an important factor when you’re trying to dial in your suspension system. This is especially true if you’re going for optimal performance.
Springs can be linear or progressive as far as their compression rate goes.
- Linear springs — linear springs offer the same rate of compression no matter how much force you apply to them. This type of spring is usually fitted on factory vehicles and is a perfectly good choice for everyday commuting.
- Progressive springs — progressive springs are a whole different beast. The idea behind this type of spring is to have different compression profiles in a single set of coil springs. Progressive springs are stiffer in one portion of their compression range, and softer in the rest.
In addition to ride comfort, your choice of springs will also dictate your ride height. Most regular cars still run a shock and spring setup where you can get an aftermarket set of springs to drop the car a few inches. In fact, performance springs are usually the first suspension upgrade most enthusiasts perform on their cars.
Springs alone are great at damping the impact of various holes and bumps, but they aren’t the best at actually forcing the wheel to maintain contact with the road. For that, you need shock absorbers.
When you hit a bump on the road, the wheel bounces up toward the body of the car. As the spring reaches full compression, it shoots the wheel back toward the road. The problem arises when the wheel hits the road and bounces back up. To stop this secondary bounce, automotive engineers have developed shock absorbers.
Shock absorbers use a hydraulic piston system to neutralize the vertical momentum of a wheel and ensure the wheel makes contact with the road as soon as it goes over a bump. Ideally, you’d want to have a suspension setup where the spring and shock have absorbed the entirety of the vertical acceleration of the wheel, allowing it to simply roll over the obstacle without unsettling the passenger cabin. This same principle was used by NASA to dampen the momentum of the launch pad swing arm during mission launches.
One of the more recent evolutions of shock absorber technology is the coilovers or coil-over-shock absorber. In essence, a coilover represents a coil spring that is integrated into the shock absorber. That way you’re getting a slimmer profile, but more importantly, you’re getting a fine-tuned piece of suspension that can be further dialed in as you see fit.
Most modern coilovers are considered a performance suspension upgrade and are generally available in the aftermarket only. That being said, there are exceptions that exist in the form of niche performance cars.
Sprung VS. Unsprung Weight
Now that we’ve gone over the most important parts of any suspension system, let’s discuss some of the most common terms you’ll run into when discussing car suspension. Sprung and unsprung weight is definitely on the list of hot topics.
Sprung weight is everything that sits on springs. That means your car’s chassis, body, engine, transmission, interior — the whole nine yards. This is the mass that presses the car against the road. Sprung weight, or more accurately mass is useful mass. In other words, if you want to get rid of mass to make your car lighter, start with unsprung weight first.
Unsprung weight is everything that sits on the other side of your car’s springs. We’re talking wheels, brake rotors, tires, calipers, control arms, and more. By keeping this weight as low as possible, you’re allowing your suspension to react faster since it’s working against less mass and hence weaker inertial forces.
A light wheel will be much easier to control on the vertical axis than a heavy one. To reduce unsprung weight, you can start by getting a set of lightweight forged wheels and a good set of performance tires.
Dependent VS Independent Car Suspension
Dependent and independent suspension are terms that tell you whether each wheel has its own suspension setup, or whether both wheels are linked by a solid axle. With front-wheel-drive cars, the front suspension is always independent, while many manufacturers utilize dependent suspension in the rear. Doing things this way brings down manufacturing costs and generally simplifies things.
That being said, there are plenty of cars that utilize independent suspension, either double-wishbone or McPherson, in both the front and the rear of the vehicle.
Every type of suspension can be tuned in a way that alters its geometry. Camber is one of the few factors that affect suspension geometry, as well as your ability to corner. Wheel camber represents the angle at which the wheel is contacting the road. As it so happens, no wheel is perfectly perpendicular to the road.
In fact, every wheel has either positive or negative camber. To understand what each of these terms mean in practice, you need to stand in front of your car. Negative camber means that your wheels are sitting at an angle where the top of the wheel is tucked in towards the engine, while the bottom part of the wheel is flaring out. For positive camber, just reverse the picture.
Negative camber is necessary to ensure that your tire is making full contact with the road as your car enters a corner and body roll shifts mass to one side of the vehicle. That being said, too much negative camber will reduce the contact patch of your tires and impact the handling capabilities of your car.
The Importance of Properly Tuned Car Suspension
Altering the suspension geometry can greatly reduce its effectiveness. Because of that, you need to make sure that your stock suspension is within spec. If you’re going for aftermarket suspension, make sure that you have a plan.
To find the best suspension components for your vehicle, head over to our online store and input your car’s details into our system. Once it’s done crunching the data, you’ll be presented with a list of products that fit your vehicle’s make and model.